Abstract

Bulk fuel was produced from spent coffee grounds (SCG) using different oil extraction and fuel production methods. The highest oil yield (30.2%) and energy efficiency (50%) from continuous hydrothermal liquefaction (CHTL) of the SCG, in water as a solvent, also had the lowest calorific value (37.4 MJ/kg). Oil from traditional hexane oil extraction had the highest calorific value (HHV) (38.7 MJ/kg). Renewable diesel yields through hydrotreatment of extracted oils were consistently higher than biodiesel yields through enzymatic transesterification of the same oils. The highest renewable diesel yield (15.8%) from batch HTL derived bio-oil had the highest calorific value (46.2 MJ/kg). However, the highest kerosene yield (9%) was obtained from in situ renewable diesel production through direct hydrotreatment of the SCG. The study showed that hydrothermal liquefaction was more efficient in producing oil from SCG than traditional solvent extraction but at the cost of losing valuable phytosterols present in the feedstock. As a bulk fuel, renewable diesel had a higher energy value than biodiesel, making it easier to blend into existing transportation fuels. The study provides useful information for the development of a sustainable waste-based bio-refinery in terms of attainable yields and processing options.

摘要

散装燃料是使用不同的油提取和燃料生产方法从废咖啡渣 (SCG) 生产的。以水为溶剂的 SCG 连续水热液化 (CHTL) 的产油率最高 (30.2%) 和能源效率 (50%) 也最低 (37.4 MJ/kg)。来自传统己烷油提取的油具有最高的热值 (HHV) (38.7 MJ/kg)。通过提取油的加氢处理获得的可再生柴油产量始终高于通过对相同油进行酶促酯交换获得的生物柴油产量。来自批次 HTL 衍生的生物油的最高可再生柴油产量 (15.8%) 具有最高的热值 (46.2 MJ/kg)。然而，最高的煤油产率 (9%) 是从原位获得的通过对 SCG 的直接加氢处理生产可再生柴油。该研究表明，与传统的溶剂萃取相比，水热液化从 SCG 生产油的效率更高，但代价是原料中存在的有价值的植物甾醇会流失。作为一种散装燃料，可再生柴油比生物柴油具有更高的能源价值，因此更容易与现有的运输燃料混合。该研究在可达到的产量和加工选择方面为可持续的基于废物的生物精炼厂的发展提供了有用的信息。